Manchester United target Jackson Martinez has agreed a deal in principle to join Arsenal in the summerReuters

Arsenal have reportedly stunned Manchester United after agreeing a deal in principle for Porto forward Jackson Martinez.

According to the Telegraph, the Gunners have met the striker's release clause, which was set at £24.8m and will sign him in the coming weeks.

Arsene Wenger had indicated that he is willing to spend money if the right player became available and with the north London failing to score a goal in their last three home games, it is believed that the Frenchman would look at adding a top quality forward to the squad.

Martinez has been impressive for the Portuguese club in recent seasons, and this campaign saw him score 32 goals for the Primeira Liga runners-up. This has prompted Wenger to make an early move for the forward, who could be an ideal addition to challenge Olivier Giroud for the central striking role.

This will come as a big blow for the Red Devils, as it was reported that Louis van Gaal was pondering a move after sending scouts to watch the striker earlier in the season.

The Old Trafford side are also in the market for a striker after seeing Robin van Persie and Radamel Falcao fail to live up to expectations this season.

Moreover, the Porto's director Fernando Gomes has admitted that the striker will be allowed to leave the club this summer, as they will be powerless to stop him if an interested club meets his release clause.

"Players have termination clauses which, if a club matches FC Porto can not stop. Everyone knows what has been said in relation to Jackson. We'll see what will happen in the future. Of course, to have financial success, which is based the sporting success, FC Porto need to buy well and sell better," Porto director Gomes said, as quoted by Noticias.